1. Field of the Invention
The present invention relates to a gas laser apparatus having a laser power supply device for exciting a laser gas in a discharge tube by producing an electric discharge therein and a blower for supplying a laser gas into the discharge tube, and more particularly to a gas laser apparatus equipped with a power calculation unit for calculating power consumed during operation.
2. Description of the Related Art
Today, there is an increasing need to reduce energy consumption in various technical fields. The field of gas laser apparatus is no exception, and the need to reduce power consumption during operation as much as possible has also been increasing in this field. In a gas laser apparatus, a laser gas is supplied into a discharge tube, and laser light is produced by exciting the laser gas in an electric discharge produced by applying a radio-frequency voltage between the electrodes inside the discharge tube. For this purpose, the gas laser apparatus incorporates in its power supply system a laser power supply device for exciting the laser gas in the discharge tube by producing an electric discharge therein and a driving device for driving a blower for supplying the laser gas into the discharge tube.
To measure the power consumption of such a gas laser apparatus, providing a power meter on the three-phase power input side of the gas laser apparatus has been proposed, as disclosed in Japanese Unexamined Patent Publication No. 2011-028372.
On the other hand, while an inverter control method is generally employed to drive the motor of the blower inside the gas laser apparatus, as a method for measuring the power consumption of a motor in general, including but not limited to a blower motor, a method that calculates the power consumption value of the motor by using the current value and voltage value respectively detected by a current detection circuit and voltage detection circuit provided on the three-phase power input side of the motor has been proposed, as disclosed in Japanese Unexamined Patent Publication No. 2010-074918.
There a control apparatus for calculating power consumption in an industrial machine having a mechanical device driven by a motor has also been proposed, as disclosed in Japanese Unexamined Patent Publication No. 2010-115063. According to this method, the power consumption of the motor is estimated through calculation by using a motor current detection unit for detecting the current flowing in the motor in conjunction with a motor rotational speed detection unit for detecting the rotational speed of the motor.
On the other hand, a method for calculating the power consumption of a power supply device by estimation from an output power value by using the output power versus conversion efficiency characteristics prestored in a storage unit has been proposed.
As described above, one possible method for measuring the power consumption of a gas laser apparatus is to install a power meter, but this method is costly and laborious. For example, according to the techniques disclosed in above-cited Japanese Unexamined Patent Publication Nos. 2011-028372 and 2010-074918, a current transformer (CT) or a power meter or the like has to be installed on a cable through which power is supplied to the gas laser apparatus.
On the other hand, if the technique disclosed in above-cited Japanese Unexamined Patent Publication No. 2010-115063 is applied to calculate the power consumption of a gas laser apparatus, it may be possible to calculate the power consumption of the blower motor by suitably combining the motor current detection unit and the motor rotational speed detection unit, but when measuring the power consumption of the gas laser apparatus, it is difficult to accurately measure it because the discharge load impedance of the discharge tube varies widely depending on the magnitude of the output of the gas laser apparatus. The technique disclosed in Japanese Unexamined Patent Publication No. 2010-115063 is therefore not suitable for measuring the overall power consumption of the gas laser apparatus.
The technique disclosed in above-cited Japanese Unexamined Patent Publication No. 2011-048548, on the other hand, requires detailed data of the output power versus conversion efficiency characteristics in order to accurately calculate the power consumption, and the capacity of the storage unit for storing the data will be enormous. The amount of computation will also be enormous.